Multivariate regional statistical models were developed to estimate flood peak values of various return periods in the Peninsular Malaysia. Annual maximum flood peak data were collected, screened, and analyzed to identify the river gauging stations' potential to produce identical flood frequency curves. The Peninsula was divided into 10 flood regions. The mean annual flood (MAF) for each region was considered as the function of catchment area (A) and mean annual rainfall (MAR). The regional equations exhibited good coefficient of determination (R-2). Except for the west of Johor Baru State (Region F6), which showed an R-2 value of 0.874, other regions had values greater than 0.90. The regions located along the eastcoast of the Peninsula exhibited better coefficients of determination compared with those for the westcoast, owing to the influence of the northeast monsoon along the eastcoast. Mean index errors (MIEs) with respect to the actual MAF of each flood region are provided to rationalize the design flood peak values to minimize the uncertainty in the predictions. Flood frequency values for the lower, mean, and upper limits were proposed to reduce the effect of outliers and uncertainty in prediction of flood peak values. Knowing the catchment area and MAR of the regions, the design flood peaks of various frequencies can be estimated for the rural ungauged catchments in the Peninsula. DOI:10.1061/(ASCE)HE.1943-5584.0000464. (C) 2012 American Society of Civil Engineers.

Regional maps and equations for the magnitude and frequency of 1, 7 and 30-day low flows were derived and are presented in this paper. The river gauging stations of neighbouring catchments that produced similar low flow frequency curves were grouped together. As such, the Peninsular Malaysia was divided into seven low flow regions. Regional equations were developed using the multivariate regression technique. An empirical relationship was developed for mean annual minimum flow as a function of catchment area, mean annual rainfall and mean annual evaporation. The regional equations exhibited good coefficient of determination (R-2 > 0.90). Three low flow frequency curves showing the low, mean and high limits for each region were proposed based on a graphical best-fit technique. Knowing the catchment area, mean annual rainfall and evaporation in the region, design low flows of different durations can be easily estimated for the ungauged catchments. This procedure is expected to overcome the problem of data unavailability in estimating low flows in the Peninsular Malaysia. (C) 2009 Elsevier B.V. All rights reserved.

Isohyetal maps were prepared to estimate Probable Maximum Precipitation (PMP) for long duration storms in Peninsular Malaysia. Historical storms of 1, 3 and 5-day durations from 21 rainfall recording stations operated by Malaysian Meteorological Service (MMS) were identified and analysed to calculate the PMP vales. Maximum rainfall for 1, 3 and 5-day storms in the Peninsula were recorded as 809, 1272.9 and 1494 mm, respectively. The widely used and most reliable hydrometeorological method was used to derive and transpose the PMP values from the storm locations to all MMS stations in the Peninsula. Maximum transposed PMP for a particular duration was obtained for six selected historical storms. Rectified Skew Orthomorphic (RSO) coordinates of the rainfall stations and point PMP values were used for the Kriging method to generate the PMP envelop curves. The enveloping isohyetal lines were further adjusted and smoothen to consider the effect of topographical and geographical effect on the PMP values. Calculated point PMP values for 1, 3 and 5-day storms can, respectively, be as high as 1149, 1808 and 2121 mm in West Malaysia. These isohyetal maps shall give direct and fast estimate for PMP values even for the catchments where no rainfall gauging stations are available. However, results obtained in this study is applicable for the catchments located at elevation lower than 200 m mean sea level (MSL), and until any storm larger than the selected (in this study) occur in Peninsular Malaysia.